Regulation of biofilm formation in Staphylococcus aureus

葡萄球菌是与植入式医疗器械相关的感染的主要原因。生物膜的产生是这类感染发病机制的一个重要方面。多糖-1,6-连接n -乙酰氨基葡萄糖（PNAG）对金黄色葡萄球菌和共凝酶阴性葡萄球菌（ConNS）的生物膜形成至关重要，它是由细胞间粘附（ica）位点编码的蛋白质合成的。本研究的目的是表征金黄色葡萄球菌中ica位点调控的机制。表皮葡萄球菌构成性地形成生物膜，而金黄色葡萄球菌在典型的体外条件下不产生PNAG，而是需要刺激，如缺铁或0.5%葡萄糖。临床分离的金黄色葡萄球菌MN8发生了自发突变，导致PNAG的组成性过量产生。在本研究的第一部分，将pnag构成菌株（MN8m）的ica位点的DNA序列与pnag诱导菌株的DNA序列进行比较，并通过Northern分析和ica启动子结合蛋白的DNA亲和力来评估MN8m ica的能力。最后，在小鼠肾脏感染模型中比较MN8m与pnag诱导金黄色葡萄球菌菌株的毒力。

The staphylococci are the leading cause of infections related to implantable medical devices. Biofilm production is an important aspect of the pathogenesis of such infections. The polysaccharide beta-1,6- linked N-acetylglucosamine (PNAG) is critical to biofilm elaboration in both Staphylococcus aureus and co-agulase-negative staphylococci (ConNS) and is synthesized from proteins encoded in the intercellular adhesion (ica) locus. The goal of this study is to characterize the mechanism through which the ica locus is regulated in S. aureus. Whereas S. epidermidis elaborates biofilm constitutively, S. aureus does not produce PNAG under typical in vitro conditions but requires a stimulus, such as iron deprivation or >0.5% glucose. A clinical isolate of S. aureus, MN8, underwent a spontaneous mutation resulting in constitutive over-production of PNAG. In the first part of this study, the DNA sequence of the ica locus from the PNAG-constitutive strain (MN8m) will be compared with that of PNAG-inducible strains of S. aureus and the ability of MN8m ica will e assessed by Northern analysis and via DNA affinity of ica promoter-binding proteins. Finally, virulence of MN8m will be compared with that of PNAG-inducible strains of S. aureus in the mouse model of renal infection.